<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
</head>

<body>
    <div id="app">
        <input type="text" v-focus />
    </div>
    <script src="./vue.js"></script>
    <script>
        Vue.directive('focus', {
            inserted: function(el) {
                el.focus();
            },
        });
        var vm = new Vue({
            el: ' #app ',
            data: {},
        });
    </script>
</body>

</html>